It turns out that g_stat() breaks apart when using 64 bit stat on
32-bit systems. Since the actual type of GStatBuf is decided when
glib/gstdio.h is included, it is thus possible for GLib itself to
be compiled with a different type than user code.
Ouch. Unfortunately going back to plain stat() also means that we
lose Unicode filename support on Windows.
Since Autoconf places some important feature flags only into the
configuration header, it is necessary to include it globally to
guarantee a consistent build.
A few of these were pretty serious, like missing arguments,
passing integers where a string was expected, and so on.
In some places, change the types used by the code rather than
just the format strings.